Like Helicopters?
Migrating Canadian geese fly over a farmer's field on Nov. 13, 2007 in New Berlin, Wisc. Biologists have fought long and sometimes bitterly about how birds evolved. In the latest argument, researchers draw an analogy between bird flight and the helicopter. Choppers can ascend and dive vertically. But this agility does not depend on the angle of attack of the rotor blades, which in fact move within a very restricted arc.